Telescope Reviews: Re: Very Best Greases for Focusers, Bearings and more

Thanks Barry and Edd -- I would likely have the pro servicing done on my Q, but I have two other fancy maks which could use some grease attention on focuser screw, focuser linear tube, worm gears, ball bearings and more and another large scope project with quite large ball transfer bearings (for azimuth), tapered roller bearings (using hidden fork stop steering head Harley bearings), numerous crossed roller bearings, and large 1.5" needle bearing on a big scope I am building for my observatory.

So, with a little more help (from all here) and research, I've decided what I do and don't want in my grease: Let's start with the what I don't want first....
1. I don't want color which can stain fingers and clothes -- either white or clear is good.
2. I don't want odor. (The grease on my Terabeam/Meade focuser AND mounts is thick, black and it smells nasty - clearly a petroleum-base gunk).
3. I don't want grease which dries out and gets sticky and gummy -- ever.
4. I don't want grease which drips oil like some cheap lithium greases I've seen - would make a mess.
What I do want in a grease is this:
1. Must be useable (minimal viscosity change) in cold temps down to 0 degrees F
2. Must allow for smoothest movement of focusers and bearings no matter what the materials riding against each other (stainless on stainless can gall pretty easily or steel on aluminum).
3. Must have truly superior rust protection - to protect my corrosion resistant, but not fully stainless, tool-steel crossed roller bearings and other bearings.
4. Preferably non-toxic.
5. Great whetting action without migrating (I want it to lubricate where I put it, but not to go onto other surfaces over time just because I happen to carry the scope in a case boucing in my car for 2000 miles from time to time).
6. I would prefer a grease where one can use very little and that's all that's needed -- not so much to save grease as to allow bearings to move without restriction caused by too much grease gunking-up the response time.
7. Must have particles sufficiently small as to not degrade performance (bind-up) my Parker and Bosch Rex Star Linear crossed roller bearings.
8. It must not degrade in any performance area listed above no matter how long (with the possible exception of requiring cleaning due to contamination from dust every few years, where exposure to dust is an insoluble problem.

Having done a bit more research, I am firmly committed to the idea that at the least, I would use either (third choice) Dupont Teflon Bearing Grease (no longer made, but still available at a few bike shops online), or (second choice) Dupont Krytox GPL 220 to 223(low viscosity, low temp., anti-corrosion) or Krytox 283az which is about the same but mil-spec and much more expensive or (first choice) is a new Dupont Krytox "XP" series, like their XP2A5 which has new soluble protection agents instead of the insoluble agents used in their 283AZ and GPL 220 series greases.
The Krytox are so totally inert, they have an unlimited shelf life and practically an unlimited service life in low stress applications, like ours. The XP stands for extra protection and compared with earlier anti-corrosion Krytox formulas relying on insoluble (suspended particles) agents, uses a fully soluble agent which has proven effective in passing the most rigorous salt water rust tests with no rust seen on the protected steel parts.

So, for now, I will try to buy some Krytox XP2A5 from the only source I can find -- http://www.tmcindustries.com/krytox_xp.html

Will let all know how it works out - should be interesting. I plan to do my own rust test with it, as well as test it's lubricity, ease of application and so on.

--------------------
Charles

2X Meade/Terabeam ETX-125 variants w/DDII Control
A few more Meade ETX-125AT UHTC
Just one APM/TMB 80/480 LZOS Super APO, FT Focuser
Working on 8"f/12 D&G folded bino-refractor
Denk binoviewers until work is done on above
Still working on elevated observatory/spaceship

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